Dr. Sesha Kiran Kollipara, Senior Scientist (Plant Pathology), Horticulture Research Station, Dr. YSR Horticultural University), Madanapalle, Andhra Pradesh, explains the current status of insects, pests, and diseases of tomato.
Madanapalle in Andhra Pradesh has the largest tomato market yard with congenial climate and water availability throughout the year, and the products go to other states and countries. But tomato, like any other solanaceous crop, is prone for pests and diseases. It is a host for many fungal, bacterial, and viral diseases. There are a few major pests that cause havoc in tomato cultivation.
First one is the fruit fly which we are familiar seeing in mango orchards causing major damage due to the continuous cultivation of mangoes and tomatoes in the mango orchards. The pest has diverted its host range from mango to tomato also. In the early stages, the adult female fruit fly lays eggs under the skin of small green tomatoes. As the tomato grows, the larva starts feeding on the pulp of tomato. Once the larva stage is over, it drops into the soil, pupae will hatch and move on to the next stage to become adult fruit fly. The fruits damaged by fruit fly look faded. When the incidence of fruit flies are not noticed in the initial stage itself, the problem magnifies. The flies can migrate to several kilometres making it difficult for the farmers. The lifecycle is short, and they can produce thousands of adults within a short time to damage the fruits in large scale. The damaged fruits are not fit for consumption and so are thrown away. This type of discarding the fruits is also dangerous as the eggs, larva, pupa, and adults are there in these fruits. They can move to the neighbouring fields and spread. The losses can go up to 100% also. The best management practice is to use pheromone, a technology approved by the government which is based on the sex hormone of the female insect. The insect releases this chemical which attracts the males to copulate to produce the next generation. So, a similar pheromone is synthetically produced in the labs in small tubes, we use the yellow sticky trap with this chemical in the field to catch sucking pests randomly which get attracted to the colour. We can then destroy the insects. Now an advanced version of pheromone exploitation for controlling pests has come up. The nano pheromone in small tubes into which small holes are made, and it slowly releases into the field and atmosphere. The adult males get attracted and get stuck on the sticky trap. The yellow sticky trap has glue on which the legs or wings get stuck. We need not use any insecticide. In this way, we deprive the females of males, no copulation takes place, and the generation comes to an end. There will not be any further production.
The next one is American Pinworm or Tuta absoluta, which has become a serious problem in the last 4 to 5 years. It was earlier thought to be tomato leaf miner as the symptoms were similar to that, but later it was found to be a different one, as this enters the fruits and damages them. It is called invasive pest from other countries, and when neglected or appropriate action not taken, the damage can be 100%. It affects solanaceous crops. The larva starts scraping the surface, eat it, enters into the inner layers of leaf, and it develops blot type of mining on the leaf. It enters into the fruit also. Then the larva stage is completed, leaves faecal matter into the fruits and comes out. The pupa will pupate into adult fly making a hole in the fruit. It spreads to create secondary infection. Again these fruits are unfit for consumption. The pupae come out of the fruits, fall on the soil, and adults come out of the fruit surface making a hole. The whole process takes about 20 to 30 days. IIHR has come out with research and management practices by testing many chemicals at different doses and combinations of insecticides that farmers are familiar with. We basically have to destroy and burn away these infected plants as they may harbour the pests of various stages. Pupae will undergo hibernation once they fall into the soil, we have to plough the field to expose the pupae to the sun and destroy them. We can also use pheromone traps to lure the males and prevent copulation. There are some eco-friendly approaches like neem oil and Azadirachtin that can be sprayed on the plant to destroy the eggs and larva. We can use a very less quantity and use the yellow sticky trap. Eppendorf tube filled with pheromone and with small holes release the chemical. It will be sensed by the males and make them get trapped on the sticky patches. This is used in many fields now, and farmers are able to get good yield and quality fruits and good amount too after selling them. The pheromone trap with sticky trap costs Rs. 60 with the tube, and we can place 2 to 3 per acre initially. If the pests are increasing, then we can more traps. There is no need for any insecticide.
Helicoverpa is another pest that enters the fruit and causes damage. It is like American pinworm, feeding on the tender foliage, make holes, enter plant, and fruit. When they fall on the soil, they pupate and transform into adult ones. We can see the eggs on the surface. When it is not controlled in the initial stage, it is difficult to destroy them using insecticide also. We can use Trichogramma one lakh per hectare at an interval of 7 days from flower initiation stages. Azadirachtin, a neem based formulation can be sprayed on the leaves to get rid of the insects. Bacillus thuringiensis can help. We can have marigold as border crop and act as deterrent of the pests. We can also use insecticides like Indoxacarb. There is no side effect or toxicity usually. We can also use funnel traps to lure the males and destroy them.
There are some major diseases also, like early blight, later blight and so on. The early blight affect the foliage, the leaves get spots which become necrotic, get detached, and drop off. Since the fruits get exposed to sunlight and the loss of leaves, they are of poor quality. It is difficult to identify if it is an early blight or later one. Early blight brings in spots on the leaves with concentric rings light and dark brown in colour. We can see these symptoms on the foliage and stem, and it will affect the fruits which whither off. There are different species of disease which cause more diseases like Alternaria solani. The farmers have to take up destroying the debris of the crop after cultivation. Lot of infected pathogen propagules like mycelium will be in the soil. They survive in the soil, and s o we have to burn the debris to reduce the pathogen load in the soil. We have to work on integrated disease management practice where we collect the debris, burn it, and use non-pesticidal approach like pheromone, plant extracts like the one from neem. The pesticides have a long time toxicity. The residue of the pesticide is harmful and is carcinogenic. So chemical pesticide should be used only when all the options have failed. We should wait for the toxicity to go from the produce and then harvest them. Destruction of infected plant material, use of healthy seeds that have gotten seed treatment, are healthy habits. Or we can use different combinations of pesticides that are commercially available. Carbendazim and mancozeb are used. We can use copper oxychloride, blitox, etc., at a lower dosage. The strobilurin based molecules can be used for more effective treatment. Many such fungicides are highly effective than the earlier ones.
Damping off is another disease in the nursery bed with sick soil infected by fungus. The seedlings die in bunches, and till we get good healthy seedlings we should not cultivate in this field. We should take care of the plants in the nursery stage itself. Post emergent damping happens, when the seedlings emerge out of the soil, and the pathogen attacks later. The collar region is rotten, and we can see lot of hollow or empty patches because of the pathogen in the soil killing them. we can use Trichoderma, Pseudo derma, and farm yard manure with neem cake to take care of the seedlings. We can also use mancozeb and copper oxychloride in the nursery bed to kill the pathogen.
Buck eye rot is seen at the harvesting stage when we see black necrotic patches on the fruits. Within a short time the fruits are affected as it spreads rapidly. We can see the mycelial growth on the surface of the fruits and flowers. This grows faster during high moisture level and low temperatures. We have to burn the debris to prevent the pathogen spreading in other stages. Metalaxyl and Cymoxanil can be used at lower dosages. Broader spacing gives better penetration of sunlight into the field. Deuteromycotina is an imperfect fungi causing small spots and necrotic path on the inner surface of the leaves, we can see yellow colour hollow on the surroundings. The leaves will wither if adequate care is not taken. There will be less production of fruits and poor quality. When the next seeding is done, fi the pathogen propagules are present in the debris, they access the plants immediately and affect them. Continuous monocropping is not recommended to prevent the pathogens from using the plants as hosts, and inoculum load will be reduced over a period of time.
Good fungicides, integrated pest management, using plastic mulching on the surface of the soil, can prevent the plants from getting affected by the pests. We can make holes on the mulches for planting. We can use sprinkler system for watering, crop rotation is needed, debris should be burnt, and these will take care of the diseases.
Fusarium is another dreadful disease which spreads within a very short time. Symptoms include wilting of the plant due to the pathogens which block the vascular tissues from roots to the leaves preventing supply of nutrients. Even if we water, the pathogens spread through the water to the adjoining fields also. The pathogens perform well in alkaline conditions. We have to raise the pH, follow crop rotation, and if the soil is affected, we should not cultivate solanaceous plants for a few years.
What are the prevalent insects and pests affecting tomato crops?
Pinworm, fruit fly are the major ones, pink ball worm, helicoverpa, are a few major pests. Right now, American pinworm is causing devastation up to 100%. The farmers have to use light traps, pheromone traps, and sticky traps. Community approach is essential to prevent the pests spreading to other fields. Pheromone traps are highly effective and available at a low cost.
What is the current status of viral diseases affecting the tomato crops?
Leaf virus, leaf curl, and yellow leaf curl, diseases like tomato mosaic, and thrip contacted viruses, are there. Last year, in both Maharashtra and Karnataka, the tomato crop was affected by many viruses, and the yield was low leading to very high prices. We had to place yellow and blue sticky traps to prevent attack by pests and viruses. In tomatoes, there is no attack of aphids.
What are the challenges faced by farmers by spider mites in tomato cultivation?
Only in case of neglected plants, spider mites attack, but tomato is a very good vegetable. Farmers are learning to be more vigilant, take care of them. Spider mites are not a major problem most of the times.
Are there any immunity strategies employed to combat fungal diseases in tomatoes?
Early blight and late blight are the major concerns. Innovative approaches being followed. Earlier people used chlorothalonil in low dosages, but now molecules that are bacteria based are being used for good results. We should not use the same insecticide repeatedly as the insects develop immunity to them. We have to follow burning the debris, crop rotation, summer ploughing and using biocontrol agents.
Any advancement in biological control of tomato pests?
The soil borne diseases are taken care of by Trichoderma, Pseudo Monas, and Bacillus. We have to use measures based on the type of disease and pest attack. Late blight is too quick to take measures to prevent. Farmers are forced to look for alternative crops to earn some money. Most of the diseases are devastating, such as fungal wilts, bacterial wilts, etc. Tomato is a highly commercial crop, needs good management, and when the infestation is there, we cannot recover our investment also. It is a risky crop. We have to take care by using biocontrol agents, damping level, and use solutions as per the type of insects or pests.
Dr. Sesha Kiran Kollipara
Senior Scientist (Plant Pathology)
Horticulture Research Station
(Dr. YSR Horticultural University)
Madanapalle, Chittoor Dt, Andhra Pradesh.
E-Mail: seshakiran.kollipara@gmail.com
Madanapalle in Andhra Pradesh has the largest tomato market yard with congenial climate and water availability throughout the year, and the products go to other states and countries. But tomato, like any other solanaceous crop, is prone for pests and diseases. It is a host for many fungal, bacterial, and viral diseases. There are a few major pests that cause havoc in tomato cultivation.
First one is the fruit fly which we are familiar seeing in mango orchards causing major damage due to the continuous cultivation of mangoes and tomatoes in the mango orchards. The pest has diverted its host range from mango to tomato also. In the early stages, the adult female fruit fly lays eggs under the skin of small green tomatoes. As the tomato grows, the larva starts feeding on the pulp of tomato. Once the larva stage is over, it drops into the soil, pupae will hatch and move on to the next stage to become adult fruit fly. The fruits damaged by fruit fly look faded. When the incidence of fruit flies are not noticed in the initial stage itself, the problem magnifies. The flies can migrate to several kilometres making it difficult for the farmers. The lifecycle is short, and they can produce thousands of adults within a short time to damage the fruits in large scale. The damaged fruits are not fit for consumption and so are thrown away. This type of discarding the fruits is also dangerous as the eggs, larva, pupa, and adults are there in these fruits. They can move to the neighbouring fields and spread. The losses can go up to 100% also. The best management practice is to use pheromone, a technology approved by the government which is based on the sex hormone of the female insect. The insect releases this chemical which attracts the males to copulate to produce the next generation. So, a similar pheromone is synthetically produced in the labs in small tubes, we use the yellow sticky trap with this chemical in the field to catch sucking pests randomly which get attracted to the colour. We can then destroy the insects. Now an advanced version of pheromone exploitation for controlling pests has come up. The nano pheromone in small tubes into which small holes are made, and it slowly releases into the field and atmosphere. The adult males get attracted and get stuck on the sticky trap. The yellow sticky trap has glue on which the legs or wings get stuck. We need not use any insecticide. In this way, we deprive the females of males, no copulation takes place, and the generation comes to an end. There will not be any further production.
The next one is American Pinworm or Tuta absoluta, which has become a serious problem in the last 4 to 5 years. It was earlier thought to be tomato leaf miner as the symptoms were similar to that, but later it was found to be a different one, as this enters the fruits and damages them. It is called invasive pest from other countries, and when neglected or appropriate action not taken, the damage can be 100%. It affects solanaceous crops. The larva starts scraping the surface, eat it, enters into the inner layers of leaf, and it develops blot type of mining on the leaf. It enters into the fruit also. Then the larva stage is completed, leaves faecal matter into the fruits and comes out. The pupa will pupate into adult fly making a hole in the fruit. It spreads to create secondary infection. Again these fruits are unfit for consumption. The pupae come out of the fruits, fall on the soil, and adults come out of the fruit surface making a hole. The whole process takes about 20 to 30 days. IIHR has come out with research and management practices by testing many chemicals at different doses and combinations of insecticides that farmers are familiar with. We basically have to destroy and burn away these infected plants as they may harbour the pests of various stages. Pupae will undergo hibernation once they fall into the soil, we have to plough the field to expose the pupae to the sun and destroy them. We can also use pheromone traps to lure the males and prevent copulation. There are some eco-friendly approaches like neem oil and Azadirachtin that can be sprayed on the plant to destroy the eggs and larva. We can use a very less quantity and use the yellow sticky trap. Eppendorf tube filled with pheromone and with small holes release the chemical. It will be sensed by the males and make them get trapped on the sticky patches. This is used in many fields now, and farmers are able to get good yield and quality fruits and good amount too after selling them. The pheromone trap with sticky trap costs Rs. 60 with the tube, and we can place 2 to 3 per acre initially. If the pests are increasing, then we can more traps. There is no need for any insecticide.
Helicoverpa is another pest that enters the fruit and causes damage. It is like American pinworm, feeding on the tender foliage, make holes, enter plant, and fruit. When they fall on the soil, they pupate and transform into adult ones. We can see the eggs on the surface. When it is not controlled in the initial stage, it is difficult to destroy them using insecticide also. We can use Trichogramma one lakh per hectare at an interval of 7 days from flower initiation stages. Azadirachtin, a neem based formulation can be sprayed on the leaves to get rid of the insects. Bacillus thuringiensis can help. We can have marigold as border crop and act as deterrent of the pests. We can also use insecticides like Indoxacarb. There is no side effect or toxicity usually. We can also use funnel traps to lure the males and destroy them.
There are some major diseases also, like early blight, later blight and so on. The early blight affect the foliage, the leaves get spots which become necrotic, get detached, and drop off. Since the fruits get exposed to sunlight and the loss of leaves, they are of poor quality. It is difficult to identify if it is an early blight or later one. Early blight brings in spots on the leaves with concentric rings light and dark brown in colour. We can see these symptoms on the foliage and stem, and it will affect the fruits which whither off. There are different species of disease which cause more diseases like Alternaria solani. The farmers have to take up destroying the debris of the crop after cultivation. Lot of infected pathogen propagules like mycelium will be in the soil. They survive in the soil, and s o we have to burn the debris to reduce the pathogen load in the soil. We have to work on integrated disease management practice where we collect the debris, burn it, and use non-pesticidal approach like pheromone, plant extracts like the one from neem. The pesticides have a long time toxicity. The residue of the pesticide is harmful and is carcinogenic. So chemical pesticide should be used only when all the options have failed. We should wait for the toxicity to go from the produce and then harvest them. Destruction of infected plant material, use of healthy seeds that have gotten seed treatment, are healthy habits. Or we can use different combinations of pesticides that are commercially available. Carbendazim and mancozeb are used. We can use copper oxychloride, blitox, etc., at a lower dosage. The strobilurin based molecules can be used for more effective treatment. Many such fungicides are highly effective than the earlier ones.
Damping off is another disease in the nursery bed with sick soil infected by fungus. The seedlings die in bunches, and till we get good healthy seedlings we should not cultivate in this field. We should take care of the plants in the nursery stage itself. Post emergent damping happens, when the seedlings emerge out of the soil, and the pathogen attacks later. The collar region is rotten, and we can see lot of hollow or empty patches because of the pathogen in the soil killing them. we can use Trichoderma, Pseudo derma, and farm yard manure with neem cake to take care of the seedlings. We can also use mancozeb and copper oxychloride in the nursery bed to kill the pathogen.
Buck eye rot is seen at the harvesting stage when we see black necrotic patches on the fruits. Within a short time the fruits are affected as it spreads rapidly. We can see the mycelial growth on the surface of the fruits and flowers. This grows faster during high moisture level and low temperatures. We have to burn the debris to prevent the pathogen spreading in other stages. Metalaxyl and Cymoxanil can be used at lower dosages. Broader spacing gives better penetration of sunlight into the field. Deuteromycotina is an imperfect fungi causing small spots and necrotic path on the inner surface of the leaves, we can see yellow colour hollow on the surroundings. The leaves will wither if adequate care is not taken. There will be less production of fruits and poor quality. When the next seeding is done, fi the pathogen propagules are present in the debris, they access the plants immediately and affect them. Continuous monocropping is not recommended to prevent the pathogens from using the plants as hosts, and inoculum load will be reduced over a period of time.
Good fungicides, integrated pest management, using plastic mulching on the surface of the soil, can prevent the plants from getting affected by the pests. We can make holes on the mulches for planting. We can use sprinkler system for watering, crop rotation is needed, debris should be burnt, and these will take care of the diseases.
Fusarium is another dreadful disease which spreads within a very short time. Symptoms include wilting of the plant due to the pathogens which block the vascular tissues from roots to the leaves preventing supply of nutrients. Even if we water, the pathogens spread through the water to the adjoining fields also. The pathogens perform well in alkaline conditions. We have to raise the pH, follow crop rotation, and if the soil is affected, we should not cultivate solanaceous plants for a few years.
What are the prevalent insects and pests affecting tomato crops?
Pinworm, fruit fly are the major ones, pink ball worm, helicoverpa, are a few major pests. Right now, American pinworm is causing devastation up to 100%. The farmers have to use light traps, pheromone traps, and sticky traps. Community approach is essential to prevent the pests spreading to other fields. Pheromone traps are highly effective and available at a low cost.
What is the current status of viral diseases affecting the tomato crops?
Leaf virus, leaf curl, and yellow leaf curl, diseases like tomato mosaic, and thrip contacted viruses, are there. Last year, in both Maharashtra and Karnataka, the tomato crop was affected by many viruses, and the yield was low leading to very high prices. We had to place yellow and blue sticky traps to prevent attack by pests and viruses. In tomatoes, there is no attack of aphids.
What are the challenges faced by farmers by spider mites in tomato cultivation?
Only in case of neglected plants, spider mites attack, but tomato is a very good vegetable. Farmers are learning to be more vigilant, take care of them. Spider mites are not a major problem most of the times.
Are there any immunity strategies employed to combat fungal diseases in tomatoes?
Early blight and late blight are the major concerns. Innovative approaches being followed. Earlier people used chlorothalonil in low dosages, but now molecules that are bacteria based are being used for good results. We should not use the same insecticide repeatedly as the insects develop immunity to them. We have to follow burning the debris, crop rotation, summer ploughing and using biocontrol agents.
Any advancement in biological control of tomato pests?
The soil borne diseases are taken care of by Trichoderma, Pseudo Monas, and Bacillus. We have to use measures based on the type of disease and pest attack. Late blight is too quick to take measures to prevent. Farmers are forced to look for alternative crops to earn some money. Most of the diseases are devastating, such as fungal wilts, bacterial wilts, etc. Tomato is a highly commercial crop, needs good management, and when the infestation is there, we cannot recover our investment also. It is a risky crop. We have to take care by using biocontrol agents, damping level, and use solutions as per the type of insects or pests.
Dr. Sesha Kiran Kollipara
Senior Scientist (Plant Pathology)
Horticulture Research Station
(Dr. YSR Horticultural University)
Madanapalle, Chittoor Dt, Andhra Pradesh.
E-Mail: seshakiran.kollipara@gmail.com